1. Field of the Invention
The invention relates to a fresh vegetable product which has a relatively long shelf life and low content of sulfiting agents (such as sodium bisulfite) and to a method (or process) of production thereof. The invention also relates to a chemical mixture used in the process for making the fresh vegetable product.
2. Background of the Invention
From the moment of harvest, vegetables undergo progressive deterioration which results in the progressive loss of taste and appearance. Efforts have been made in the past to prolong the time that vegetables retain their fresh taste and appearance. Such efforts have included refrigerating vegetables and treating them with preservatives. The deterioration of taste and appearance is accelerated when a vegetable is subdivided, such as by cutting, or otherwise physiologically injured, for example, by removing its skin. A brown or black discoloration may appear at the site of the cut or injury within a relatively short period of time. The discoloration of vegetables as a result of subdivision and possible other preparations for human consumption is a problem of significant economic importance in the food industry. The discoloration of such vegetable matter is unsightly and unappetizing and is associated in the public's mind with distastefully old vegetables, which are perceived to be unsuitable for consumption.
This problem has become more pronounced as the demand for fresh whole and subdivided vegetables has been steadily increasing over the years due to the popularity of salad bars in eating establishments and consumers' demand for convenience food items. Such convenience items include whole and subdivided vegetables which, as purchased, are suitable for consumption, or for further processing by consumers. Further processing by consumers includes, for example, cooking or grilling of the vegetables.
The increased consumer demand for greater availability of such fresh, whole and subdivided vegetables immediately suitable for consumption or further processing has been underscored by the consumers' health consciousness. Consumers demand the availability of fresh, whole and subdivided vegetables which retain their fresh taste and do not have a substantially higher calorie or fat content than freshly harvested vegetables. Thus, consumers express a strong preference for fresh instead of frozen or deep fried vegetables. Several proposals have been made for providing fresh (not frozen) subdivided vegetables which retain their fresh appearance and flavor. For example, it has been proposed to vacuum-cool produce where it is cooled in a reduced pressure environment prior to packaging. Such a method lengthens the shelf life of the produce and may slow the growth of bacteria and fungi. However, this method is relatively expensive.
Bell, U.S. Pat. No. 5,226,972, suggests washing subdivided fresh produce with water that preferably comprises an oxidizing agent, such as chlorine or a chloride, at a sufficiently high temperature and for a time sufficient to remove such deterioration-causing agents as bacteria and fungi and liquids and solids emitted by the produce itself. The wash water temperature is preferably about 55.degree. to about 70.degree. F.
It has also been proposed to contact subdivided, fresh produce with numerous agents, e.g., sulfiting agents, such as sodium bisulfite, in relatively large amounts, such that the final vegetable product has a sulfite concentration of about 10 percent by weight. However, the use of such relatively large amounts of bisulfite imparts undesirable off-taste to the vegetables. As a result, relatively large amounts of sugar, such as dextrose, have to be added to the vegetables to neutralize the off-taste. The large amounts of sugar, in turn, impart an undesirable sweet taste to the vegetables.
Various other agents and processes have been proposed for minimizing spoilage and browning of vegetables. Thus, Beck, U.S. Pat. No. 5,126,153, and Beck, U.S. Pat. No. 5,389,389, disclose methods for treating produce to minimize browning upon subsequent processing, handling and/or storage including exposing the produce (such as fruits and vegetables, e.g., potatoes) to discoloration inhibitors, including cysteine, calcium chloride, sodium acid pyrophosphate, and/or a sulfiting agent in such amounts that a treated product contains less than about 30 ppm sulfite and preferably less than about 10 ppm or essentially no sulfite. After the treatment with the discoloration inhibitors, the product is preferably subjected to a dehydration step to form a dehydrated, storage-stable product.
Dickerson, et. al., U.S. Pat. No. 5,425,308, discloses an apparatus and method for slicing potatoes and washing or coating potato slices with water or a solution of various known treating materials, such as chemical preservatives, e.g., bisulfite, additives, etc. The apparatus and method include two concentric rings (FIGS. 1 and 4) which spray high pressure water or a solution of chemicals. The resulting washed, cut potatoes are usually conveyed to a next processing station, usually a fryer or oven.
Gardner et. al., U.S. Pat. No. 4,988,523, disclose a process for treating fresh peeled potatoes and other peeled vegetables and fresh peeled fruits, including preserving the vegetables or fruits, by a first dipping process or spraying, employing a mixture of a commercial preservative, e.g., SPORIX.TM., and citric acid. After trimming, the peeled vegetables or fruits are subjected to a second exposure of the same solution and thereafter they are packaged and refrigerated for up to 12 days without exhibiting discoloration or purification. According to Gardner et al., SPORIX.TM. is characterized as an acid sodium metaphosphate.
Weiss et. al., U.S. Pat. No. 5,162,127, disclose a process for treating foodstuffs subject to oxidative or enzymatic discoloration, such as fruits, vegetables, and cereal grains, comprising contacting such foodstuffs with an aqueous solution of a hydrolysis mixture of aldonic acid and its lactones or a precursor thereof and very small quantities of a sulfiting agent. The processing usually takes place at an ambient temperature of about 50-70.degree. F., but elevated temperatures may also be utilized, e.g., 110.degree. or even 180.degree. F.
Cherry, et. al., U.S. Pat. No. 4,937,085, discloses the treatment of white, cut potatoes to prevent blackening thereof. The treatment includes contacting the white, cut potatoes with a combination of citric acid and cysteine. The combination optionally also includes ethylenediamine tetraacetic acid (EDTA).
However, none of the methods discussed above provides fresh (i.e., not previously frozen) vegetables that are cleaned, and that substantially taste like fresh vegetables even after a relatively long period of time, and that are suitable for immediate consumption by the consumer or for further processing.